The Food and Drug Administration plans to loosen the rules for approving new treatments for Alzheimer's disease.

Drugs in clinical trial would qualify for approval if people at very early stages of the disease subtly improved their performance on memory or reasoning tests, even before they developed any obvious impairments. Companies would not have to show that the drugs improved daily, real-world functioning.

For more than a decade, the only way to get Alzheimer’s drugs to market was with studies showing that they improved the ability of patients not only to think and remember, but also to function day to day at activities like feeding, dressing or bathing themselves.

The proposal, published online Wednesday in The New England Journal of Medicine, could help millions of people at risk of developing the disease by speeding the development and approval of drugs that might slow or prevent it.

The proposed policy could also be a boon for the pharmaceutical industry and researchers. They have often felt stymied by regulations that left them uncertain of how to get drugs tested and approved for marketing to people early in the course of Alzheimer’s, when the medications are most likely to be useful.

Several studies are being planned for people at high risk of developing Alzheimer’s, and the proposed regulations should lead to even more clinical trials, said Dr. P. Murali Doraiswamy, an Alzheimer’s researcher and professor of psychiatry at Duke University School of Medicine.

“There is more motivation now to invest in the field,” Dr. Doraiswamy said. But, he added, the proposal also comes with risks.